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Body Logistics > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What is digestion?

A

Physical and chemical disruption of food for absorption of nutrients

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2
Q

What are the 4 accessory organs to the digestive system?

A

Salivary glands, gall bladder, pancreas, liver

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3
Q

Name 6 things about saliva

A

1) Contains amylase and lipase
2) Bacteriostatic (IgA)
3) High calcium (protects teeth)
4) Alkaline
5) Assists swallowing
6) Protects the mouth

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4
Q

What are the four layers of gut wall? Which is the layer where arteries/veins/glands and nerves are found? What are the other layers made up of?

A

Mucosa
Sub mucosa
Muscular externae
Serosa

Mucosa - stratified squamous non-keratinised epithelium and lamina propria (CT)

Sub Mucosa is connective tissue where arteries/veins/glands and nerves are found

Muscular externae has 2 layers of smooth muscle - outer longitudinal, inner circular

Serosa made up of simple squamous epithelium and connective tissue

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5
Q

8 functions of the GI tract? (think from mouth down)

A

1) Entry of food
2) Disrupt food
3) Store food
4) Digest food
5) Kill pathogens
6) move food along
7) Absorb nutrients
8) Eliminate waste

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6
Q

What 5 groups of nutrients do we need to absorb?

A 
Vitamins 
Minerals
Fatty acids
Amino Acids
Sugars
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7
Q

What does saliva contain to make it bacteriostatic?

A

Immunoglobulin A antibody

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8
Q

What 2 enzymes does saliva contain

A

Lipase Amylase

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9
Q

How does a bolus get swallowed?

A

Initial voluntary muscle contraction of oesophagus, then involuntary, rapid peristaltic movement

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10
Q

Where is the fastest GI transport?

A

Entry exit - rest is comparatively low

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11
Q

What is oesophageal epithelium and why is it well suited?

A

Stratified squamous epithelium non keratinised - can withstand abrasion

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12
Q

Where do you find lamina propria in the body?

A

Mucosal areas - e.g. GI, Lung, GU

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13
Q

What is the lamina propria? What does it contain?

A

Thin layer of loose connective tissue or dense irregular connective tissue laying under the epithelium. This plus epithelium (+/- muscle) = mucosal membrane. Contains Peyer’s patches

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14
Q

How does mechanical and chemical disruption of food begin in the mouth?

A

Mastication

Amylase/lipase

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15
Q

What is a role of the muscularis externae layer of gut wall?

A

Peristalsis

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16
Q

How does the stomach aid physical and chemical digestion?

A

Physical - Churning - 3 muscle layers and rugae

Chemical - Add HCl and Pepsin

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17
Q

Why do we need the stomach to be a temporary food store?

A

Can eat faster than we can digest

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18
Q

How does the stomach not digest itself

A

Mucus

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19
Q

What is chyme? Is it Hypo or hypertonic?

A

acid, enzymes, partially digested food that has been agitated by stomach. It is hypertonic

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20
Q

What are the roles of HCl and Pepsin in the stomach?

A

Protein breakdown - pepsin

Disinfect food - HCl

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21
Q

What 5 cells are in a gastric gland in the stomach? What do they do?

A

Goblet like cells - secret mucus
Stem cells - regenerate
Parietal cells - secrete H+ into lumen and HCO3- into capillaries which move it to surface mucous cells
Chief cells - secrete pepsinogens –> pepsins
Enteroendocrine cells - secrete gastrin (hormone that stimulates acid secretion)

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22
Q

What are the roles of the duodenum (6)

A

Draw in water and neutralise chyme (isotonic) with bicarbonate rich mucus, absorb iron. Receives bile from gallbladder. Pancreas and liver secrete alkali to neutralise acidic chyme. Pancreas, liver and intestine secrete specific enzymes which act with bile to complete digestion of chyme.

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23
Q

What glands secrete bicarb rich mucus from duodenum?

A

Brunner’s glands

24
Q

What do the pancreas and liver secrete into the duodenum (2)?

A

alkali, enzymes

25
Q

What do the enzymes from pancreas and intestine do (4)?

A

Cleave peptides to amino acids
Cleave polysaccharides to monosaccharides
Break down and reform lipids
Break down nucleic acids

26
Q

Is absorption passive or active

A

active

27
Q

How does the jejunum maximise surface area (2)?

A
  • place circulares

- villi

28
Q

What is the epithelium of the jejunum? What other cell is there?

A

Simple columnar with goblet cells and villi

29
Q

What is a lacteal?

A

Dilated lymphatic vessel

30
Q

Whats the function of the jejunum?

A

Absorbs most sugars, aa’s, fatty acids

31
Q

What does the ileum do?

A

Absorbs vit12, bile acids and remaining nutrients

32
Q

By end of ileum what still needs to happen?

A

Water needs to be reabsorbed - colon

33
Q

Whats the order of the colon starting with caecum?

A

Caecum, ascending, transverse, descending, sigmoid

34
Q

What is the function of colon?

A

Absorb water and electrolytes

35
Q

What are Crypts of Lieberkuhn

A

Simple columnar epithelium in crypts - glands - cells produce a lot of mucus, absorb water and electrolytes among other things

36
Q

How long is the transit in colon?

A

20 hours

37
Q

Where do contents await expulsion?

A

in colon NOT rectum

38
Q

Where is most bacteria held in GI? is it anaerobic or aerobic? Where is it lost?

A

Colon, 99% anaerobic and lost in faeces

39
Q

What are the functions on bacteria in colon? (3)

A

1) Synthesis of vitamins K, B12 etc (absorbed by colon)
2) Breakdown of primary to secondary bile acids (absorbed by colon)
3) Conversion of bilirubin to non pigmented metabolites that are reabsorbed in the colon

40
Q

How is the GI controlled? (3)

A

Endocrine
Nervous
Paracrine (esp stomach)

41
Q

How is the GI tract controlled by nervous system?

A

Somatic- mouth, swallowing, anus

Autonomic - peristalsis

42
Q

How many nerve plexuses are there along the GI tract?

A

2

43
Q

Which two paracrine substances control GI? What do they do?

A

Histamine - controls acid production in stomach

Vasoactive substances - affect blood flow in gut

44
Q

What are the three major endocrine substances that control the GI?

A

1) Gastrin -
2) CCK (Chlycystokinin)
3) Secretin

45
Q

What is gastrin and what does it do (1) ? Where is it released from?

A

Hormone stimulates secretion of HCl from parietal cells in the stomach. Released from G cells of pyloric antrum of stomach, pancreas and duodenum

46
Q

What is CCK and what does it do (3) ? Where is it secreted?

A

Hormone - secreted by enteroendocrine cells of the duodenum. Hunger suppressant. Promotes release of enzymes from pancreas, bile from gallbladder

47
Q

What is secretin? What does it do (3)

A

Hormone - promotes bicarb secretion from duct cells of pancreas, promotes bile production by liver, inhibits secretion of acid by parietal cells of stomach.

48
Q

Where is bit B12 absorbed from?

A

Ileum

49
Q

Where is Iron absorbed from?

A

Duodenum

50
Q

Where are electrolytes absorbed from?

A

Colon

51
Q

Where are AA, fatty acids and carbs absorbed from?

A

Jejunum

52
Q

Where are bile acids and remaining nutrients absorbed from?

A

Ileum

53
Q

What are Peyers patches?

A

Aggregations of lymphocytes present in the Lamina Propia

54
Q

What are two sources of innervation to the gut located in the gut wall?

A

Myenteric Plexus

Submucosal Plexus

55
Q

What three things is bile made up of?

A

Bile salts
Water
Alkali

56
Q

How long is the duodenum and what shape?

A

20-25cm shortest part and C shaped

Body Logistics (8 decks)

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